1 //===- CallGraphSCCPass.cpp - Pass that operates BU on call graph ---------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the CallGraphSCCPass class, which is used for passes
11 // which are implemented as bottom-up traversals on the call graph. Because
12 // there may be cycles in the call graph, passes of this type operate on the
13 // call-graph in SCC order: that is, they process function bottom-up, except for
14 // recursive functions, which they process all at once.
16 //===----------------------------------------------------------------------===//
18 #define DEBUG_TYPE "cgscc-passmgr"
19 #include "llvm/CallGraphSCCPass.h"
20 #include "llvm/IntrinsicInst.h"
21 #include "llvm/Function.h"
22 #include "llvm/PassManagers.h"
23 #include "llvm/Analysis/CallGraph.h"
24 #include "llvm/ADT/SCCIterator.h"
25 #include "llvm/ADT/Statistic.h"
26 #include "llvm/Support/CommandLine.h"
27 #include "llvm/Support/Debug.h"
28 #include "llvm/Support/Timer.h"
29 #include "llvm/Support/raw_ostream.h"
32 static cl::opt<unsigned>
33 MaxIterations("max-cg-scc-iterations", cl::ReallyHidden, cl::init(4));
35 STATISTIC(MaxSCCIterations, "Maximum CGSCCPassMgr iterations on one SCC");
37 //===----------------------------------------------------------------------===//
40 /// CGPassManager manages FPPassManagers and CallGraphSCCPasses.
44 class CGPassManager : public ModulePass, public PMDataManager {
47 explicit CGPassManager(int Depth)
48 : ModulePass(&ID), PMDataManager(Depth) { }
50 /// run - Execute all of the passes scheduled for execution. Keep track of
51 /// whether any of the passes modifies the module, and if so, return true.
52 bool runOnModule(Module &M);
54 bool doInitialization(CallGraph &CG);
55 bool doFinalization(CallGraph &CG);
57 /// Pass Manager itself does not invalidate any analysis info.
58 void getAnalysisUsage(AnalysisUsage &Info) const {
59 // CGPassManager walks SCC and it needs CallGraph.
60 Info.addRequired<CallGraph>();
61 Info.setPreservesAll();
64 virtual const char *getPassName() const {
65 return "CallGraph Pass Manager";
68 virtual PMDataManager *getAsPMDataManager() { return this; }
69 virtual Pass *getAsPass() { return this; }
71 // Print passes managed by this manager
72 void dumpPassStructure(unsigned Offset) {
73 errs().indent(Offset*2) << "Call Graph SCC Pass Manager\n";
74 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
75 Pass *P = getContainedPass(Index);
76 P->dumpPassStructure(Offset + 1);
77 dumpLastUses(P, Offset+1);
81 Pass *getContainedPass(unsigned N) {
82 assert(N < PassVector.size() && "Pass number out of range!");
83 return static_cast<Pass *>(PassVector[N]);
86 virtual PassManagerType getPassManagerType() const {
87 return PMT_CallGraphPassManager;
91 bool RunAllPassesOnSCC(CallGraphSCC &CurSCC, CallGraph &CG,
92 bool &DevirtualizedCall);
94 bool RunPassOnSCC(Pass *P, CallGraphSCC &CurSCC,
95 CallGraph &CG, bool &CallGraphUpToDate,
96 bool &DevirtualizedCall);
97 bool RefreshCallGraph(CallGraphSCC &CurSCC, CallGraph &CG,
101 } // end anonymous namespace.
103 char CGPassManager::ID = 0;
106 bool CGPassManager::RunPassOnSCC(Pass *P, CallGraphSCC &CurSCC,
107 CallGraph &CG, bool &CallGraphUpToDate,
108 bool &DevirtualizedCall) {
109 bool Changed = false;
110 PMDataManager *PM = P->getAsPMDataManager();
113 CallGraphSCCPass *CGSP = (CallGraphSCCPass*)P;
114 if (!CallGraphUpToDate) {
115 DevirtualizedCall |= RefreshCallGraph(CurSCC, CG, false);
116 CallGraphUpToDate = true;
120 TimeRegion PassTimer(getPassTimer(CGSP));
121 Changed = CGSP->runOnSCC(CurSCC);
124 // After the CGSCCPass is done, when assertions are enabled, use
125 // RefreshCallGraph to verify that the callgraph was correctly updated.
128 RefreshCallGraph(CurSCC, CG, true);
135 assert(PM->getPassManagerType() == PMT_FunctionPassManager &&
136 "Invalid CGPassManager member");
137 FPPassManager *FPP = (FPPassManager*)P;
139 // Run pass P on all functions in the current SCC.
140 for (CallGraphSCC::iterator I = CurSCC.begin(), E = CurSCC.end();
142 if (Function *F = (*I)->getFunction()) {
143 dumpPassInfo(P, EXECUTION_MSG, ON_FUNCTION_MSG, F->getName());
144 TimeRegion PassTimer(getPassTimer(FPP));
145 Changed |= FPP->runOnFunction(*F);
149 // The function pass(es) modified the IR, they may have clobbered the
151 if (Changed && CallGraphUpToDate) {
152 DEBUG(dbgs() << "CGSCCPASSMGR: Pass Dirtied SCC: "
153 << P->getPassName() << '\n');
154 CallGraphUpToDate = false;
160 /// RefreshCallGraph - Scan the functions in the specified CFG and resync the
161 /// callgraph with the call sites found in it. This is used after
162 /// FunctionPasses have potentially munged the callgraph, and can be used after
163 /// CallGraphSCC passes to verify that they correctly updated the callgraph.
165 /// This function returns true if it devirtualized an existing function call,
166 /// meaning it turned an indirect call into a direct call. This happens when
167 /// a function pass like GVN optimizes away stuff feeding the indirect call.
168 /// This never happens in checking mode.
170 bool CGPassManager::RefreshCallGraph(CallGraphSCC &CurSCC,
171 CallGraph &CG, bool CheckingMode) {
172 DenseMap<Value*, CallGraphNode*> CallSites;
174 DEBUG(dbgs() << "CGSCCPASSMGR: Refreshing SCC with " << CurSCC.size()
176 for (CallGraphSCC::iterator I = CurSCC.begin(), E = CurSCC.end();
181 bool MadeChange = false;
182 bool DevirtualizedCall = false;
184 // Scan all functions in the SCC.
185 unsigned FunctionNo = 0;
186 for (CallGraphSCC::iterator SCCIdx = CurSCC.begin(), E = CurSCC.end();
187 SCCIdx != E; ++SCCIdx, ++FunctionNo) {
188 CallGraphNode *CGN = *SCCIdx;
189 Function *F = CGN->getFunction();
190 if (F == 0 || F->isDeclaration()) continue;
192 // Walk the function body looking for call sites. Sync up the call sites in
193 // CGN with those actually in the function.
195 // Get the set of call sites currently in the function.
196 for (CallGraphNode::iterator I = CGN->begin(), E = CGN->end(); I != E; ) {
197 // If this call site is null, then the function pass deleted the call
198 // entirely and the WeakVH nulled it out.
200 // If we've already seen this call site, then the FunctionPass RAUW'd
201 // one call with another, which resulted in two "uses" in the edge
202 // list of the same call.
203 CallSites.count(I->first) ||
205 // If the call edge is not from a call or invoke, then the function
206 // pass RAUW'd a call with another value. This can happen when
207 // constant folding happens of well known functions etc.
208 CallSite::get(I->first).getInstruction() == 0) {
209 assert(!CheckingMode &&
210 "CallGraphSCCPass did not update the CallGraph correctly!");
212 // Just remove the edge from the set of callees, keep track of whether
213 // I points to the last element of the vector.
214 bool WasLast = I + 1 == E;
215 CGN->removeCallEdge(I);
217 // If I pointed to the last element of the vector, we have to bail out:
218 // iterator checking rejects comparisons of the resultant pointer with
226 assert(!CallSites.count(I->first) &&
227 "Call site occurs in node multiple times");
228 CallSites.insert(std::make_pair(I->first, I->second));
232 // Loop over all of the instructions in the function, getting the callsites.
233 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
234 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
235 CallSite CS = CallSite::get(I);
236 if (!CS.getInstruction() || isa<DbgInfoIntrinsic>(I)) continue;
238 // If this call site already existed in the callgraph, just verify it
239 // matches up to expectations and remove it from CallSites.
240 DenseMap<Value*, CallGraphNode*>::iterator ExistingIt =
241 CallSites.find(CS.getInstruction());
242 if (ExistingIt != CallSites.end()) {
243 CallGraphNode *ExistingNode = ExistingIt->second;
245 // Remove from CallSites since we have now seen it.
246 CallSites.erase(ExistingIt);
248 // Verify that the callee is right.
249 if (ExistingNode->getFunction() == CS.getCalledFunction())
252 // If we are in checking mode, we are not allowed to actually mutate
253 // the callgraph. If this is a case where we can infer that the
254 // callgraph is less precise than it could be (e.g. an indirect call
255 // site could be turned direct), don't reject it in checking mode, and
256 // don't tweak it to be more precise.
257 if (CheckingMode && CS.getCalledFunction() &&
258 ExistingNode->getFunction() == 0)
261 assert(!CheckingMode &&
262 "CallGraphSCCPass did not update the CallGraph correctly!");
264 // If not, we either went from a direct call to indirect, indirect to
265 // direct, or direct to different direct.
266 CallGraphNode *CalleeNode;
267 if (Function *Callee = CS.getCalledFunction()) {
268 CalleeNode = CG.getOrInsertFunction(Callee);
269 // Keep track of whether we turned an indirect call into a direct
271 if (ExistingNode->getFunction() == 0) {
272 DevirtualizedCall = true;
273 DEBUG(dbgs() << " CGSCCPASSMGR: Devirtualized call to '"
274 << Callee->getName() << "'\n");
277 CalleeNode = CG.getCallsExternalNode();
280 // Update the edge target in CGN.
281 CGN->replaceCallEdge(CS, CS, CalleeNode);
286 assert(!CheckingMode &&
287 "CallGraphSCCPass did not update the CallGraph correctly!");
289 // If the call site didn't exist in the CGN yet, add it. We assume that
290 // newly introduced call sites won't be indirect. This could be fixed
292 CallGraphNode *CalleeNode;
293 if (Function *Callee = CS.getCalledFunction())
294 CalleeNode = CG.getOrInsertFunction(Callee);
296 CalleeNode = CG.getCallsExternalNode();
298 CGN->addCalledFunction(CS, CalleeNode);
302 // After scanning this function, if we still have entries in callsites, then
303 // they are dangling pointers. WeakVH should save us for this, so abort if
305 assert(CallSites.empty() && "Dangling pointers found in call sites map");
307 // Periodically do an explicit clear to remove tombstones when processing
309 if ((FunctionNo & 15) == 15)
313 DEBUG(if (MadeChange) {
314 dbgs() << "CGSCCPASSMGR: Refreshed SCC is now:\n";
315 for (CallGraphSCC::iterator I = CurSCC.begin(), E = CurSCC.end();
319 dbgs() << "CGSCCPASSMGR: SCC Refresh didn't change call graph.\n";
323 return DevirtualizedCall;
326 /// RunAllPassesOnSCC - Execute the body of the entire pass manager on the
327 /// specified SCC. This keeps track of whether a function pass devirtualizes
328 /// any calls and returns it in DevirtualizedCall.
329 bool CGPassManager::RunAllPassesOnSCC(CallGraphSCC &CurSCC, CallGraph &CG,
330 bool &DevirtualizedCall) {
331 bool Changed = false;
333 // CallGraphUpToDate - Keep track of whether the callgraph is known to be
334 // up-to-date or not. The CGSSC pass manager runs two types of passes:
335 // CallGraphSCC Passes and other random function passes. Because other
336 // random function passes are not CallGraph aware, they may clobber the
337 // call graph by introducing new calls or deleting other ones. This flag
338 // is set to false when we run a function pass so that we know to clean up
339 // the callgraph when we need to run a CGSCCPass again.
340 bool CallGraphUpToDate = true;
342 // Run all passes on current SCC.
343 for (unsigned PassNo = 0, e = getNumContainedPasses();
344 PassNo != e; ++PassNo) {
345 Pass *P = getContainedPass(PassNo);
347 // If we're in -debug-pass=Executions mode, construct the SCC node list,
348 // otherwise avoid constructing this string as it is expensive.
349 if (isPassDebuggingExecutionsOrMore()) {
350 std::string Functions;
352 raw_string_ostream OS(Functions);
353 for (CallGraphSCC::iterator I = CurSCC.begin(), E = CurSCC.end();
355 if (I != CurSCC.begin()) OS << ", ";
360 dumpPassInfo(P, EXECUTION_MSG, ON_CG_MSG, Functions);
364 initializeAnalysisImpl(P);
366 // Actually run this pass on the current SCC.
367 Changed |= RunPassOnSCC(P, CurSCC, CG,
368 CallGraphUpToDate, DevirtualizedCall);
371 dumpPassInfo(P, MODIFICATION_MSG, ON_CG_MSG, "");
374 verifyPreservedAnalysis(P);
375 removeNotPreservedAnalysis(P);
376 recordAvailableAnalysis(P);
377 removeDeadPasses(P, "", ON_CG_MSG);
380 // If the callgraph was left out of date (because the last pass run was a
381 // functionpass), refresh it before we move on to the next SCC.
382 if (!CallGraphUpToDate)
383 DevirtualizedCall |= RefreshCallGraph(CurSCC, CG, false);
387 /// run - Execute all of the passes scheduled for execution. Keep track of
388 /// whether any of the passes modifies the module, and if so, return true.
389 bool CGPassManager::runOnModule(Module &M) {
390 CallGraph &CG = getAnalysis<CallGraph>();
391 bool Changed = doInitialization(CG);
393 // Walk the callgraph in bottom-up SCC order.
394 scc_iterator<CallGraph*> CGI = scc_begin(&CG);
396 CallGraphSCC CurSCC(&CGI);
397 while (!CGI.isAtEnd()) {
398 // Copy the current SCC and increment past it so that the pass can hack
399 // on the SCC if it wants to without invalidating our iterator.
400 std::vector<CallGraphNode*> &NodeVec = *CGI;
401 CurSCC.initialize(&NodeVec[0], &NodeVec[0]+NodeVec.size());
404 // At the top level, we run all the passes in this pass manager on the
405 // functions in this SCC. However, we support iterative compilation in the
406 // case where a function pass devirtualizes a call to a function. For
407 // example, it is very common for a function pass (often GVN or instcombine)
408 // to eliminate the addressing that feeds into a call. With that improved
409 // information, we would like the call to be an inline candidate, infer
410 // mod-ref information etc.
412 // Because of this, we allow iteration up to a specified iteration count.
413 // This only happens in the case of a devirtualized call, so we only burn
414 // compile time in the case that we're making progress. We also have a hard
415 // iteration count limit in case there is crazy code.
416 unsigned Iteration = 0;
417 bool DevirtualizedCall = false;
420 dbgs() << " SCCPASSMGR: Re-visiting SCC, iteration #"
421 << Iteration << '\n');
422 DevirtualizedCall = false;
423 Changed |= RunAllPassesOnSCC(CurSCC, CG, DevirtualizedCall);
424 } while (Iteration++ < MaxIterations && DevirtualizedCall);
426 if (DevirtualizedCall)
427 DEBUG(dbgs() << " CGSCCPASSMGR: Stopped iteration after " << Iteration
428 << " times, due to -max-cg-scc-iterations\n");
430 if (Iteration > MaxSCCIterations)
431 MaxSCCIterations = Iteration;
434 Changed |= doFinalization(CG);
440 bool CGPassManager::doInitialization(CallGraph &CG) {
441 bool Changed = false;
442 for (unsigned i = 0, e = getNumContainedPasses(); i != e; ++i) {
443 if (PMDataManager *PM = getContainedPass(i)->getAsPMDataManager()) {
444 assert(PM->getPassManagerType() == PMT_FunctionPassManager &&
445 "Invalid CGPassManager member");
446 Changed |= ((FPPassManager*)PM)->doInitialization(CG.getModule());
448 Changed |= ((CallGraphSCCPass*)getContainedPass(i))->doInitialization(CG);
455 bool CGPassManager::doFinalization(CallGraph &CG) {
456 bool Changed = false;
457 for (unsigned i = 0, e = getNumContainedPasses(); i != e; ++i) {
458 if (PMDataManager *PM = getContainedPass(i)->getAsPMDataManager()) {
459 assert(PM->getPassManagerType() == PMT_FunctionPassManager &&
460 "Invalid CGPassManager member");
461 Changed |= ((FPPassManager*)PM)->doFinalization(CG.getModule());
463 Changed |= ((CallGraphSCCPass*)getContainedPass(i))->doFinalization(CG);
469 //===----------------------------------------------------------------------===//
470 // CallGraphSCC Implementation
471 //===----------------------------------------------------------------------===//
473 /// ReplaceNode - This informs the SCC and the pass manager that the specified
474 /// Old node has been deleted, and New is to be used in its place.
475 void CallGraphSCC::ReplaceNode(CallGraphNode *Old, CallGraphNode *New) {
476 assert(Old != New && "Should not replace node with self");
477 for (unsigned i = 0; ; ++i) {
478 assert(i != Nodes.size() && "Node not in SCC");
479 if (Nodes[i] != Old) continue;
484 // Update the active scc_iterator so that it doesn't contain dangling
485 // pointers to the old CallGraphNode.
486 scc_iterator<CallGraph*> *CGI = (scc_iterator<CallGraph*>*)Context;
487 CGI->ReplaceNode(Old, New);
491 //===----------------------------------------------------------------------===//
492 // CallGraphSCCPass Implementation
493 //===----------------------------------------------------------------------===//
495 /// Assign pass manager to manage this pass.
496 void CallGraphSCCPass::assignPassManager(PMStack &PMS,
497 PassManagerType PreferredType) {
498 // Find CGPassManager
499 while (!PMS.empty() &&
500 PMS.top()->getPassManagerType() > PMT_CallGraphPassManager)
503 assert(!PMS.empty() && "Unable to handle Call Graph Pass");
506 if (PMS.top()->getPassManagerType() == PMT_CallGraphPassManager)
507 CGP = (CGPassManager*)PMS.top();
509 // Create new Call Graph SCC Pass Manager if it does not exist.
510 assert(!PMS.empty() && "Unable to create Call Graph Pass Manager");
511 PMDataManager *PMD = PMS.top();
513 // [1] Create new Call Graph Pass Manager
514 CGP = new CGPassManager(PMD->getDepth() + 1);
516 // [2] Set up new manager's top level manager
517 PMTopLevelManager *TPM = PMD->getTopLevelManager();
518 TPM->addIndirectPassManager(CGP);
520 // [3] Assign manager to manage this new manager. This may create
521 // and push new managers into PMS
523 TPM->schedulePass(P);
525 // [4] Push new manager into PMS
532 /// getAnalysisUsage - For this class, we declare that we require and preserve
533 /// the call graph. If the derived class implements this method, it should
534 /// always explicitly call the implementation here.
535 void CallGraphSCCPass::getAnalysisUsage(AnalysisUsage &AU) const {
536 AU.addRequired<CallGraph>();
537 AU.addPreserved<CallGraph>();
541 //===----------------------------------------------------------------------===//
542 // PrintCallGraphPass Implementation
543 //===----------------------------------------------------------------------===//
546 /// PrintCallGraphPass - Print a Module corresponding to a call graph.
548 class PrintCallGraphPass : public CallGraphSCCPass {
550 raw_ostream &Out; // raw_ostream to print on.
554 PrintCallGraphPass() : CallGraphSCCPass(&ID), Out(dbgs()) {}
555 PrintCallGraphPass(const std::string &B, raw_ostream &o)
556 : CallGraphSCCPass(&ID), Banner(B), Out(o) {}
558 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
559 AU.setPreservesAll();
562 bool runOnSCC(CallGraphSCC &SCC) {
564 for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I)
565 (*I)->getFunction()->print(Out);
570 } // end anonymous namespace.
572 char PrintCallGraphPass::ID = 0;
574 Pass *CallGraphSCCPass::createPrinterPass(raw_ostream &O,
575 const std::string &Banner) const {
576 return new PrintCallGraphPass(Banner, O);